1. Field of the Invention
This invention relates to two-component insulating glass adhesives/sealants based on liquid polysulfide and/or polymercaptan polymers which contain benzoates as plasticisers.
2. Discussion of Related Art
Single-/multi-component compositions based on polysulfide polymers and/or polymercaptan polymers have been used successfully for a long time in construction and civil engineering, in the aircraft and vehicle industries, in shipbuilding and on a large scale for the manufacture of insulating glass. One of the main reasons why a very high market share of insulating glass adhesives/sealants is based on polysulfide polymers or polymercaptan polymers is that these polymers are characterised by a high resistance to ozone and also very good resistance to many solvents and chemicals. In addition, they have a very high long-term resistance to the effects of weather and are characterised by very low permeability to gases. For more information on this, see, for example, A. Damusis, “Sealants”, New York (1967), pages 182-184; E. Dachselt, “Thioplaste” Leipzig (1971), pages 50-56 or H. Lucke, “Aliphatische Polysulfide”, Heidelberg (1992), pages 111-114.
Adhesives/sealants for insulating glass composite materials are usually formulated as two-component systems in which the two components are brought together, mixed and applied only just before use.
In this type of two-component material, one component usually contains the binder, in this case a liquid polysulfide polymer or liquid polymercaptan polymer. This component is usually termed component “A”. The second component contains a cross-linking, curing or oxidising agent and is usually termed component “B”. Furthermore, both components generally contain plasticisers, fillers and optionally pigments or colorants. In addition, component A may also contain adhesion-promoting substances and antioxidants and component B may also contain accelerators.
The number of plasticisers which are compatible with polysulfide polymers or polymercaptan polymers is very limited. Apart from a small number of phthalates, chlorinated paraffins, butyl diglycols or hydrogenated terphenyls may be used in two-component adhesives/sealants based on polysulfides or polymercaptans. Chlorinated paraffins are not generally used now, for environmental reasons. Apart from compatibility and resistance to ageing, plasticisers which are suitable for insulating glass adhesives/sealants also have to have a very low vapor pressure so that condensation is not formed in the insulating glass unit. This means that the insulating glass unit has to have “fog-free” or “non-fogging” properties. Furthermore, the plasticiser has to have sufficiently high viscosity to prevent the powdered components, in particular in component B, settling out, so that phase separation does not occur during the time the components are stored. This restricts the selection of suitable plasticisers very considerably so that from among the esters of phthalic acid, butylbenzyl phthalate is now used almost exclusively in component A and the highly viscous plasticiser 7-(2,6,6,8-tetramethyl-4-oxa-3-oxononyl)-benzyl phthalate, also known by the tradename “Santicizer 278” (Solutia Co.), is used in component B.
Recently, a few study groups have indicated that phthalates may exert an endocrinal effect in the uterus and that the sperm counts in male offspring may be reduced. Benzylbutyl phthalate is also mentioned expressly in this connection. For more information, see, for example, the publications by R. M. Sharpe, N. E. Skakkebaek; “Are oestrogens involved in falling sperm counts and disorders of the male reproductive tract?”, Lancet 341 (1993), p. 1392-1395. Also, more recent publications on the Internet by P.M.D. Foster, http://www.ciit.org/ACT97/ACTIVITIESSEPT97/sept97.html and by R. M. Sharpe, J. S. Fisher, Mike M. Millar, S. Jobling and John P. Sumpter, http://ehpnet1.niehs.nih.gov/docs/1995/103-12/sharpe.html indicate similar risks which are attributed to phthalate plasticisers.
It has not hitherto been possible to exclude highly viscous phthalates from component B of insulating glass adhesives/sealants because, on the one hand, these are compatible with the polysulfide polymers or polymercaptan polymers used and prevent settling out of the disperse constituents and, on the other hand “fogging” is avoided. A disadvantage of using so-called highly viscous phthalates has been firstly that they are very difficult to pump and secondly that it is difficult to mix the two components A and B thoroughly during application.
Thus, an object of the present invention is to find a plasticiser for two-component adhesives/sealants based on polysulfide polymers and/or polymercaptan polymers which does not have the disadvantages of the prior art described above and about which no negative biological effects are known.